A half-hour north of us in Bellingham, students at Western Washington University's Vehicle Research Institute are working on one potential transportation future. Several years ago, they built Viking 32, a hybrid-electric sports car fueled by compressed biogas from the nearby VanderHaak anaerobic digester.
Next, the team plans to scale up the biogas-filtering system to provide fuel for buses. In rough terms, the annual biogas yield from one cow's manure is equal to 150 gallons of diesel, so there's definitely a transportation opportunity. The WWU students will primarily be working through other issues, such as cleaning and pressurizing the gas economically. Overall, society will have to decide when to embrace compressed natural gas as a vehicle fuel.